Manning's roughness coefficient values for some common materials

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Manning's roughness coefficient values are used in the Manning's formula for flow calculation in open flow channels. Coefficients for some common used surface materials can be found in the table below:

Surface Material

Manning's Roughness Coefficient - n -

Asbestos cement

0.011

Asphalt

0.016

Brass

0.011

Brick

0.015

Canvas

0.012

Cast-iron, new

0.012

Clay tile

0.014

Concrete - steel forms

0.011

Concrete (Cement) - finished

0.012

Concrete - wooden forms

0.015

Concrete - centrifugally spun

0.013

Copper

0.011

Corrugated metal

0.022

Earth, smooth

0.018

Earth channel - clean

0.022

Earth channel - gravelly

0.025

Earth channel - weedy

0.030

Earth channel - stony, cobbles

0.035

Floodplains - pasture, farmland

0.035

Floodplains - light brush

0.050

Floodplains - heavy brush

0.075

Floodplains - trees

0.15

Galvanized iron

0.016

Glass

0.010

Gravel, firm

0.023

Lead

0.011

Masonry

0.025

Metal - corrugated

0.022

Natural streams - clean and straight

0.030

Natural streams - major rivers

0.035

Natural streams - sluggish with deep pools

0.040

Natural channels, very poor condition

0.060

Plastic

0.009

Polyethylene PE - Corrugated with smooth inner walls

0.009 - 0.015

Polyethylene PE - Corrugated with corrugated inner walls

0.018 - 0.025

Polyvinyl Chloride PVC - with smooth inner walls

0.009 - 0.011

Rubble Masonry

0.017

Steel - Coal-tar enamel

0.010

Steel - smooth

0.012

Steel - New unlined

0.011

Steel - Riveted

0.019

Vitrified Sewer

0.013 - 0.015

Wood - planed

0.012

Wood - unplaned

0.013

Wood stove pipe, small diameter

0.011 - 0.012

Wood stove pipe, large diameter

0.012 - 0.013

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Related Topics

Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.